Technical Field
The present disclosure is directed to generating power drive signals for an actuator.
Description of the Related Art
Digital cameras have progressed to smaller sizes, lower weight, and higher resolutions. A drawback to this development, however, has been the impact of minor movements on image quality. Particularly, subtle movements or vibrations while capturing an image often causes image blurring. This is especially a problem for smartphones with built-in cameras, where users capture images with outstretched arms and have a greater chance of involuntary movements. Image stabilization is widely used to minimize image blurring. Current methods of image stabilization include digital image stabilization, electronics image stabilization, and optical image stabilization. Generally, digital image stabilization and electronics image stabilization require large amounts of memory and processor resources. Optical image stabilization, on the other hand, minimizes memory and processor demands by adjusting the lens position itself. As such, optical image stabilization is ideal for portable devices, such as smartphones and tablets with built-in cameras.
In general, optical image stabilization minimizes image blurring by sensing movements of a housing and compensating for the movements by adjusting the position of the camera lens. For example, see “Optical Image Stabilization (OIS),” Rosa et al, STMicroelectronics. Optical image stabilization circuits typically include a gyroscope, a controller, and a drive circuit that includes a large current source to drive an actuator to move the camera lens.
Most drive circuits output either a linear power drive signal having a constant voltage level or a standard pulse-width modulation power drive signal having high (i.e., 1) and low (i.e., 0) voltage levels with a certain duty cycle or frequency. For example, see “Optical Image Stabilization (OIS),” Rosa et al, STMicroelectronics. Linear power drive signals and pulse-width modulation power drive signals each having their own advantages. Namely, linear power drive signals are used to reduce noise, and standard pulse-width modulation power drive signals are used for power efficiency. Drive circuits, however, generally do not generate both linear and standard pulse-width modulation power drive signals.